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Draining Filling Cooling System
 
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Pelican Technical Article:

Draining Filling Cooling System

Nick Czerula

Time:

1 hours1 hrs

Tab:

$60

Talent:

**

Tools:

Phillips screwdriver, hose clamp pliers

Applicable Models:

R56 MINI Cooper Hatchback (2007-11)
R56 MINI Cooper JCW Hatchback (2009-11)
R56 MINI Cooper S Hatchback (2007-11)

Parts Required:

Engine coolant

Hot Tip:

Work with a cool engine.

Performance Gain:

Cooling system parts lifespan increased

Complementary Modification:

Replace hoses

Engine coolant is the working fluid for the cooling system, which controls the operational temperature of the engine. Each combustion event inside your engine creates a lot of heat, and the engine needs to be at a certain temperature to operate efficiently. Engine coolant maintains about the same temperature year round, regardless of ambient temperature.

A properly maintained cooling system must have a few things in order: adequate supply of coolant, a radiator that acts as a heat exchanger with the outside air, a fan or air flow source, a water pump to keep the coolant circulating, and a thermostat to regulate the engine at its optimum operating temperature. The coolant must also have the correct mixture and chemical compounds to promote heat transfer, protect against freezing, and also inhibit corrosion. To keep your MINI operating correctly, it's important to check the level, strength, and overall condition of the coolant on a regular basis. You also need to change the coolant before it degrades to the point where it doesn't perform its job adequately.

One failure mode associated with dirty coolant is known as electrolysis. Electrolysis occurs when stray electrical current routes itself through the engine coolant. The electricity is attempting to find the shortest path, and impurities in the coolant often generate a path of least resistance that the electricity travels across. The source of this stray electricity is often from electrical engine accessories, which have not been properly grounded. A missing engine or transmission ground strap can also cause the coolant to become electrified. Sometimes the path of least resistance becomes a radiator, a heater hose, or even the heater core. These components are often well grounded, and offer a ground path from the engine to the chassis by means of the semi-conductive path of the coolant.

Electrolysis can destroy your engine quickly. Although it's semi-normal to have very small amounts of voltage potential in your coolant system, values greater than about a tenth of a volt can start reactions between the coolant and the metal in your engine. In particular, electrolysis affects primarily aluminum engine components, resulting in pitting and scaring of the aluminum surface. This eating away of the metal can cause coolant system leaks, and in particular, radiator leaks around aluminum welds. Cast-iron components are also vulnerable, but typically the aluminum metal parts fail first. On MINIs in particular, electrolysis can be easily seen attacking aluminum cylinder heads.

The process works somewhat like electrical discharge machines (EDM). These machines work by passing a large electrical current through metal, literally zapping away bits of material until nothing remains. Unfortunately, the electrolysis process works in a similar way, zapping bits of metal in proportion to the amount of electrical current passing through the coolant. A poorly grounded starter can literally destroy a radiator or head within a matter of weeks, depending upon how often the car is started. A smaller current drain, like an electric cooling fan, may slowly erode components over many months.

How can you test for electrolysis? Other than actually seeing visible signs of erosion, you can perform a current flow test. Connect the negative terminal of a voltmeter to the chassis ground. Test for adequate continuity by touching another point on the chassis. The resistance should be near to zero. With the engine cold and running, submerge the positive probe into the coolant tank, making sure that the probe does not touch any metal parts. The voltage should be less than .10 volts. If not, methodically turn off or unplug each electrical accessory until the reading reads below .10 volts. Have an assistant switch accessories (like the A/C compressor, heater blower, etc.) while you measure the voltage.

If an accessory doesn't have an on/off switch, test it by temporarily running a ground from the housing of the accessory to the chassis. Ground each component and check the voltmeter. If the wire restores a missing ground connection to the accessory, then you've found a component with a faulty ground.

During this test, be sure to check the starter. Not only will a poorly grounded starter struggle to turn over the engine, it will also zap away tremendous amounts of metal in your cooling system. Watch the meter carefully when starting the engine. Any voltage spike will indicate a faulty ground connection.

Your MINI will lose a little bit of coolant here and there over time due to evaporation from the reservoir. However, a significant loss of coolant over a very short period of time almost certainly signifies a leak in the system. Sometimes a leak can be seen when you park the car overnight. Often the coolant leaks out and then evaporates while you're driving, leaving no telltale mark of coolant on the pavement. If you suspect a coolant leak, visually inspect all of the hoses, the water pump, the reservoir, and the radiator for seepage or the 'weeping' of coolant out of seams and gaskets. Check the seal on the radiator cap. Check that the expansion tank cap is fastened securely. The way the MINI expansion tank cap is designed makes it easy to make the simple, yet deadly mistake of leaving the cap cocked - allowing coolant to leak out when the engine is running. If you suspect a leak that you cannot see, a pressure test can verify the integrity of your system. See our tech article on cooling system leak testing.

Draining and filling your cooling system is a maintenance requirement as well as being part of many repairs. Be careful when working with coolant. It is poisonous and especially dangerous for pets. Clean all spills immediately and rinse the area with water.

MINI R56 models hold about 5.2 liters of coolant.

In this article, I'll go over the steps involved with replacing the engine coolant on the MINI R56 models. Be sure to work with a cool engine and confirm the cooling system lacks pressure before opening the cooling system.

Lift and support the front of the vehicle safely. See our tech article on lifting your MINI.

To check coolant level at the expansion tank (red arrow), check the coolant level at the right side of the tank (green arrows).
Figure 1

To check coolant level at the expansion tank (red arrow), check the coolant level at the right side of the tank (green arrows). Coolant should be between the MIN and MAX markings (inset).

Draining cooling system: Working in the engine compartment, remove the expansion tank cap.
Figure 2

Draining cooling system: Working in the engine compartment, remove the expansion tank cap. Be sure that the engine has cooled before removing the cap. Cover the cap with a rag when opening. If there is still system pressure, this will lessen the spillage.

Draining cooling system: For normally aspirated models (Cooper) remove the right side splash shield (green arrow).
Figure 3

Draining cooling system: For normally aspirated models (Cooper) remove the right side splash shield (green arrow). Loosen the three Phillips head screws and remove the shield. For turbocharged models (Cooper S), remove the splash shield on the left side.

Draining cooling system: Place a five-gallon bucket (green arrow) under the radiator.
Figure 4

Draining cooling system: Place a five-gallon bucket (green arrow) under the radiator.

Draining cooling system: For normally aspirated models (Cooper), you will have to remove the right side radiator hose (area indicated by green arrow) to drain the coolant.
Figure 5

Draining cooling system: For normally aspirated models (Cooper), you will have to remove the right side radiator hose (area indicated by green arrow) to drain the coolant. The radiator shown is from a turbocharged model. The hose is in that area.

Draining cooling system: For turbocharged models (Cooper S), you will have to remove the left side radiator hose (green arrow) to drain the coolant.
Figure 6

Draining cooling system: For turbocharged models (Cooper S), you will have to remove the left side radiator hose (green arrow) to drain the coolant. Use hose clamp pliers to remove the hose clamp. Then separate the hoses.

Draining cooling system: Allow the engine coolant (green arrow) to drain completely into the drain pan (red arrow).
Figure 7

Draining cooling system: Allow the engine coolant (green arrow) to drain completely into the drain pan (red arrow). Once the coolant has stopped dripping, reinstall the radiator hose.

Filling and bleeding cooling system: Before filling, turn the ignition ON (do not start engine).
Figure 8

Filling and bleeding cooling system: Before filling, turn the ignition ON (do not start engine). Set the temperature controls in the vehicle interior to full warm and the blower fan speed to Low. Using a 50% distilled water 50% engine coolant mix, slowly fill the expansion tank until the coolant level indicator reaches MAX. The level indicator diagram is located on the tank (green arrows). Reference this when filling to obtain the correct level. Trapped air is common when filling a cooling system and can result in improper cooling. It is important to bleed your cooling system each time the cooling system is serviced. Install the expansion tank cap and be sure all bleeder screws are tight. Start and run the engine at idle until it reaches operating temperature and check the cooling level. Top it up with coolant as needed. When done, check the cooling system for leaks.

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Comments and Suggestions:
Bryson Comments: When I did my first drain the coolant was a very dark green. My replacement coolant was blue MINI brand. To be safe, I flushed it with deionized water 4 times to get all the old coolant out. One trick I learned to speed up the process was to blow air through the system using my mouth, creating a seal and pushing air in yes I know it's poisonous. I was careful. and that pushed a ton of old coolant out. I also did that when bleeding the system each time by blowing into the system with the bleeder valve open until coolant started flowing through.

From the picture:
- Sample one was from the first drain of just the old coolant.
- Sample two was after just filling it with water, bleeding and running it, and draining it again.
- Sample Three was the same deal.
- Sample four I used the "blow push" method and it helped a ton.
August 18, 2016
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Shellback Comments: I'm servicing my Wife's 2012 Cooper S for MTTS 2016. I haven't found the thermostat housing for the bleeder? I have the Bentley manual and it doesn't seem to show the bleeder as well.
June 30, 2016
  Followup from the Pelican Staff: Your vehicle may not have that bleeder. Proceed bleeding, skip opening that bleeder. - Nick at Pelican Parts  
Sebastian Comments: You say to bleed the cooling system. How exactly do you bleed the system?
May 4, 2016
  Followup from the Pelican Staff: Filling and bleeding cooling system: Before filling, turn the ignition ON (do not start engine). Set the temperature controls in the vehicle interior to full warm and the blower fan speed to Low. Using a 50% distilled water 50% engine coolant mix, slowly fill the expansion tank until the coolant level indicator reaches MAX. The level indicator diagram is located on the tank (green arrows). Reference this when filling to obtain the correct level. Trapped air is common when filling a cooling system and can result in improper cooling. It is important to bleed your cooling system each time the cooling system is serviced. Install the expansion tank cap and be sure all bleeder screws are tight. Start and run the engine at idle until it reaches operating temperature and check the cooling level. Top it up with coolant as needed. When done, check the cooling system for leaks. - Nick at Pelican Parts  
Cobraman Comments: I have a Mini Cooper s roadster. I have just replaced the water pump and I am ready to fill the cooling system. When replacing the water pump I removed the large hose from the inter cooler that goes up and across the front of the motor right side. Is the intercollegiate a separate system or is it a part of the main cooling system? I want to make sure that it is not left empty causing problems in the future.
March 29, 2016
  Followup from the Pelican Staff: The intercooler does not hold engine coolant. It is for air. - Nick at Pelican Parts  
David Comments: Hello Pelican parts, I'm very thankful for your technical articles. They are very informative. I was changing the turbo on my 2007 R56 mini and now that I'm completely done, I need to fill the coolant back up. Your article talks about bleeding the air out of the system but it doesn't show the location of the bleeder valve. Can you tell me where it is located? Thanks, David.
November 26, 2015
  Followup from the Pelican Staff: Some models have a bleeder on the thermostat, at the top. Others do not. You can bleed by filling the system as described in the article. - Nick at Pelican Parts  

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